Maintaining metallic surfaces immersed in a marine environment clear and free of deposits has long been a universal problem. Metallic surfaces made from valve metal, the so-called "film forming" metals such as titanium, tantalum, zirconium, aluminum, niobium and tungsten are, under most circumstances, quite immune to normal corrosion, and thus such materials are widely used as heat exchange surfaces. However, such surfaces as well as other electroconductive surfaces such as other metals or graphite are vulnerable to biofouling as well as mineral scaling, these deposits interfering with heat transfer, impeding fluid control, corroding the exchanger surface, and the like. Such deposits may be of the alkaline type, such as metal carbonates, or the deposit may be marine growth, such as barnacles, algae and the like. All such deposits, whether they are in a soft, semi-soft, or a hardened condition, must be removed for efficient heat exchange operations. Thus, once the deposits become a problem to heat exchanger operation, the equipment must be shut down and operations terminated until such deposits are removed from the heat exchange surfaces. Various means of removing deposits from metallic surfaces have been employed in the past. Most prominent and still prominent today is the shutting down of such fouled equipment coupled with either mechanically scraping of the deposits therefrom or acid washing of the equipment to remove such deposits. Both of these treatments entail significant equipment down-time owing to the necessity for a shutdown of the equipment. Where the deposits are the result of calcium and/or magnesium scale formation, water softeners and conditioners have been used to reduce the formation of scale. However, such means are quite expensive and are often unsuccessful at completely preventing the formation of such scale deposits.
Another method of keeping the surfaces of heat exchanger clear is by continuously subjecting said surface to chlorine or sodium hypochlorite generated in situ. Such treatment can prevent the growth of algae and barnacle formation. Normally, the chlorine is added to the system, although it can be manufactured in situ if the liquid used in the system is capable of passing a current and contains a chloride salt or other chlorine producer. Typical of such systems is an apparatus and method shown and described in U.S. Pat. No. 3,241,512 electrolytically preventing fouling of ship surfaces by the electrolysis of saltwater to produce chlorine gas distributed over the boat hull thereby keeping the hull surface clean while removing and/or preventing growth of barnacles, algae and other foreign and undesirable material. In the '512 patent, copper electrodes are utilized providing some dissolved copper ions in water surrounding the hull which assist in preventing fouling. Other prior art describes similar processes wherein dimensionally stable anodes are used for producing the chlorine in situ to prevent fouling.